Due to great potential application to flexible display devices, organic light emitting diodes (OLEDs) have recently become very important to the scientific community and the display industry, and now attract much focus in research and development. An OLED is a light-emitting diode (LED) in which a film of organic compounds is placed between two conductors and emits light in response to excitation such as by an electric current. OLEDs are useful in displays such as television screens, computer monitors, mobile phones, and tablets. OLED devices are self-luminous devices, and have been actively studied for their brightness, superior visibility, and the ability to display clearer images in comparison with liquid crystal devices.
However, the OLED device technology is currently experiencing an obstacle in the development process. A main issue is that light-emitting efficiency cannot meet practical demand, so the development of the OLED technology is greatly limited. One of the factors affecting the luminous efficiency of the OLED device is the efficiency of transporting carriers, including electrons and holes.